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Full text of "Text Book Of Mechanical Engineering"

TAe Slide Rest.

Turning to the Slide-rest and its various feed motions, details
are shewn in Pigs. 130, 131, 141, and 14.2. x is the saddle,
having one rnovernent, that along the bed; Y is the middle slide,
moving atwss the bed; and the top slide z has a universal motion,
but by hand, being mounted on a circular table formed on Y ; and
thus a feed may be obtained at any angle by turning the upper
plate z and clamping the bolts a a.

The movement of x is'called traversing or sliding, and the
cross-movement of Y surfacing; these can be combined if re-
quired- The slide rest is actuated from the mandrel in two
distinct ways. The featfmg screw at the front of the lathe bed is
only used for screw cutting, and is thus preserved from wear at
other times. It is driven by * change wheels,* at the left end of
bed (Fig. 132). These can be changed, so that various rates of
rotation of screw can be effected, relative to that of the mandrel,
which'comparison fixes the fineness of thread cut on the work.
To facilitate the fixing of the wheels chosen, the intermediate stud
b is supported (Figs. 130 and 140) on a radial arm or quadrant 4
which can be clamped at various angles, the two wheels on b being
fastened together by keying to a loose sleeve d. The saddle and
leading screw are connected or disconnected by the two half
nuts e e (shewn apart in Fig. 141), which are brought together by
moving the handle downward along the dotted arc, when the
studs J/j carrying the nuts, are brought nearer the centre by
means of the curved grooves,

The slide rest is also worked from the back shaft h on the
opposite side of the bed, and the two feeds for surfacing and
sliding obtained. The shaft is driven from the mandrel by change
wheels (shewn dotted at , Fig. 131), the intermediates being
carried on the arm c. Some makers drive by belt, which may
slip if the machine Is being overworked, but there is no doubt
that wheels give a more definite feed. Passing to the connection
of shaft with saddle we refer to Figs. 141 and 130, A worm j\
having a feather kef, slides along the back shaft, being drawn
along by the saddle. The power passes through an intermediate
worm pinion 2 to the wheel 3, which, being keyed on spindle ^,
crossing the bed, rotates pinion 4 on the front side. This pinion,
gearing into wheel 5, turns the rack pinion 6, and the traverse is